Granular material packing machines are employed to produce sand cores from very fine sand impregnated with thermo setting resin. Such apparatus typically injects the sand into a mold formed of two halves which are heated and cause the resin in the sand to be cured, resulting into a completed casting core of a desired shape for use to produce desired internal casting configurations in cast parts.
Generally, the most widely used method of introducing the core sand into the mold is by air jets which blow the sand into the core box. This widely used method causes a number of problems. One such problem is that compressed air mixed with sand erodes the core box. Where there are detailed passages in complicated cores, it eventually destroys the core box as a usable box in that the erosion of such edges causes flashing to be formed on the cores. The flashing normally requires what is referred to as "definning," which is the removal of the flashing by filing with a rasp or file. Obviously, "definning" requires a substantial amount of man hours and increases the cost of core making.
Also, blowing core sand causes the resin to separate from the sand creating free resin that sticks onto the core box. A build-up of resin on the core box results in formation of voids in the cores rendering them defective and unusable because it adversely effects the shape of the core.
The above two problems result in a number of bad cores, which are required to be thrown away. Further, the eroding of the core box and the build-up of resin on the core box requires greater maintenance and eventual replacement of the core boxes.
Another problem encountered with the use of blowing the core sand is that it erodes the seal on the blow plate, which is the plate that engages the core box.
Another problem in the blowing of core sand is the need to exhaust or vent the air from the mold. Failure to vent all the air results in air pockets which create voids in the cores.
Because of the above problems in the use of air jets to blow sand for dispensing sand into the core boxes, there has been a long-felt need for a method and apparatus for making sand cores so as to avoid or at least minimize the above problems.